Simple B&B. The Indian Army have a saying. If it ain't broke, don't fix it. Magazines are individually fitted to ensure perfect feeding of the rounds and a tight fit. As a result, they're numbered to the rifle. If they are changed for any reason, they're renumbered.
If a magazine works loose in service, then it's put in a box with a load of others and a replacement fitted until its correct, feeds and is tight, then re-numbered. After many months, the 'always loose' magazines are taken out, a small part of the rib is cut away and a new piece brazed or silver soldered in place. When the need arises, it's filed to shape and re-fitted to another rifle. That is a chore for one of the new boys or someone who has upset the ASM (the boss of the workshop) or someone who needs bringing down a peg or two!
Another little punishment was a day spent on the Armourers test range, accuracy and range testing a few hundred No5 rifles..............................